The present invention relates to centrifugal pumps, and in particular to centrifugal pumps for feeding thrust chambers of rocket engines with reducer and/or oxidizer propellants, and more particularly with cryogenic propellants.
Examples of centrifugal pumps for feeding propellants to combustion chambers of a rocket engine are disclosed in French patent application FR 2 964 425 A1. Each of those prior art centrifugal pumps has an impeller, a rotary shaft secured to said impeller, a casing with an axial admission passage, and at least one bearing supporting said rotary shaft in said casing. In order to avoid leaks in an axial direction between the casing and the rotary shaft, those centrifugal pumps also include at least one dynamic seal around the rotary shaft, the impeller being situated between the at least one dynamic seal and the axial admission passage.
Typically, during the operation of such a centrifugal pump, its impeller exerts a large axial force on the rotary shaft towards the axial admission passage of the pump. In order to enable these forces to be taken up by the bearing(s) supporting the rotary shaft, one solution that has been proposed for other prior art pumps is the solution of incorporating at least one active balancing piston with the back of the impeller. Nevertheless, such a piston has the drawback of presenting considerable bulk. On the other hand, if the bearings are dimensioned so as to be capable on their own of taking up such a considerable force, that can only be done to the detriment of the compactness of the overall assembly. In addition, taking up axial forces through bearings in that way can dissipate a large amount of power.
Another solution that has been envisaged for compensating the axial force on the impeller is to add a plate to the tips of the blades of the impeller of the centrifugal pump. Nevertheless, that solution is difficult to implement, in particular on impellers of small size.